Rolled metal strip



April 4, i967 HANssoN 3,312,538

ROLLED METAL STRIP Original Filed March 21, 1962 4 Sheets-Sheet 1 PIB4', E967 A. HANSSON 3,32,538

ROLLED METAL STRIP Original Filed March 21, 1962 4 Sheets-Sheet 2INVENTOR n.' j AN-rs Fil-Nason A ORNEYJ April 4, 1967 A. HANssoN3,312,538

ROLLED METAL STRIP original Filed March 21, 1962 4 sheets-sheet sINVENTQR AN-rs H Au ssoN ATTOR NEYS pl 4, 1967 A. HANSSON 3,312,538

ROLLED METAL STRIP' Original Filed March 2l, 1962 4 Sheets-Sheet 4INVENTOR Ann-s HANSSON ATTORNEYS United States Patent O This applicationis a division lof application Ser. No. 181,347, filed Mar. 21, 1962, nowPatent No. 3,239,922.

This invention relates to articles having a plurality of channelstherein.

An object of the invention is to provide articles which have a pluralityof internal passages separated by partitions which are integral andmonolithic with the outer walls.

A further object of the invention is to provide an article having aplurality of internal channels separated from one another by partitionwalls which are integral with the outer closing walls and haveexternally projecting fins which are also integral with the outerclosing walls.

Another object of this invention is to provide an article of manufactureconsisting of integral metal providing continuous outer walls andinternal septa defining quadrilateral internal longitudinal channels inthe article, each septum merging with an inner surface of an outer wallby a curved surface at one face of the septum, and by a reentrant angleat the other, at least one of the outer walls having fins integral withsaid wall and extending away therefrom.

Another object of this invention is to provide an article of manufacturehaving outer walls and septa integral with said walls and extendingtherebetween for defining quadrilateral internal channels and endclosures attached to said walls, some of the septa being excised at theends to provide communications between adjacent channels.

Another object `of this invention is to provide an article ofmanufacture, of the type set forth above, wherein the end excisions areat atlernate ends of adjacent septa to provide a tortuous flow passagethrough the article.

Another `object of this invention is to provide an article ofmanufacture, of the type set forth above, in which two first septaextend between the end closures, and at least one second septum islocated between the rst septa, both ends of the second septum beingexcised to provide manifold spaces adjacent the end closures.

Another object of this invention is to provide an article of manufacturecomprising spaced wall portions, septa integral with and located inparallel planes extending between the wall portions, the sidemost septabeing spaced from the edges of the wall portions parallel thereto, thewall portions between the respective sidemost septum and the adjacentedge being directed toward and into abutment and connected with oneanother.

Another object of this invention is t-o provide an article ofmanufacture comprising a rolled metal strip of essentially uniformthickness and having integral angularly directed and overlapping rstlongitudinal discontinuities between metal portions extending from sideto side of the strip, and having angularly directed llongitudinal seconddiscontinuities extending from a roller surface thereof, the seconddiscontinuities defining between them integral scales having thin edgesat the surface and being thicker at the region of integration with themetal portions overlying the integral discontinuities.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claimed subjectmatter and the 3,312,538 Patented Apr. 4, 1967 Mice several viewsillustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is an end view of a billet prepared under the practice of thisinvention;

FIGURE 2 is an end view tof a section of the Strip product made byrolling the billet of FIGURE 1;

FIGURE 3 is a like View, showing the surface separations and a partialopening of the strip of FIGURE 2;

FIGURE 4 is a like view, showing the strip opened until the septa areessentially at right angles to the surface layers;

FIGURE 5 is a like view, showing the product of trimming and joining thelateral edges of the surface;

FIGURE 6 is a sectional view substantially on line 6 6 `of FIGURE 5,with end closures in place;

FIGURE 6a is a partial sectional View substantially on line a-a ofFIGURE 6;

FIGURE 7 is a sectional view corresponding to FIG- URE 6, but showingdifferent end closures and excisions from the septa;

FIGURE 8 is a view similar to that of FIGURE 1, showing a form of billetfor providing cells in two rows;

FIGURE 9 is a view similar to that of FIGURE 2, of the strip productfrom the billet of FIGURE 8;

FIGURE 10 is a view at a larger scale showing the expansion of the stripof FIGURE 9;

FIGURE 11 is a View similar to that of FIGURE 1, showing a third form`of billet, for producing an article having a plurality of internalchannels and pluralities of external fins;

FIGURE 12 is a View similar to that of FIGURE 2, showing the stripproduct of rolling the billet of FIG- URE ll;

FIGURE 13 is a like view at a larger scale, of a part og the articlemade by expanding the strip of FIGURE 1 FIGURE 14 is a view similar tothat of FIGURE 1, showing a fourth form of billet;

- FIGURE 15 is a view similar to that of FIGURE 2, showing the stripproduct of rolling the billet of FIG- URE 14;

FIGURE 16 is a view showing an article made by eX- panding the strip ofFIGURE 15;

FIGURE 17 is a View similar to that `of FIGURE 11, showing a fth form ofbillet;

FIGURE 18 is a view similar to that of FIGURE 12, showing the stripproduct of rolling the billet of FIG- URE 17;

FIGURE 19 is a like View on a larger scale, showing an article made byexpanding the stripl of FIGURE 18;

FIGURE 20 is a View of a strip as in FIGURE 2, showing the raising of asurface scale by sh-ot peening.

In the form of practice shown in FIGURES 1 to 4, a billet 10 isprepared, illustratively of rectangular crosssection, and provided witha plurality of inclined and overlapping internal channels 11, 12, 13,14, 15, 16 which have parallel walls with original billet metal betweenpairs of the channels, as shown at 17, 18, 19, 20, 21. Therewith, thebillet has integrated solid metal lateral portions 22, 23 at its ends,and upper and lower portions 24, 25 of solid metal. The channels arewider than they are thick and extend parallel to one another along thelength of the billet. Longitudinal grooves or notches 26 are formed inthe upper and lower faces of the billet to preclude weakenings thereinin line with the outermost edges of the two sidemost channels 1.1, 16:these notches extending for, for example, about one-half of t-hethickness of the respective metal face portions 24, 25. The grooves ornotches 26 preferably have their base or root located adjacent to theend of sidemost channels 11 and 16 nearest to the respective lateraledge of the billet 10.

Such billets may be prepared by casting molten metal into a mold andaround central portions of nondbonding and removable cores positionedtherein. For example, in making an aluminum billet, the cores can be atpieces of stainless steel preferably having thin coatings of aweldpreventing material such as a refractory oxide. Such cores may besingle sheets of the cross-section for providing a respective channeland later removed by stretching until their sections are smaller thanthe respective channel in the ingot: or the cores may be composite, e.g.each being of three pieces having interlitting ribs and grooves at theirinterfaces, the central piece being convergently tapered and the sidepieces having the interfitted edges correspondingly tapered, so that thecentral piece can later be easily withdrawn and thereby free the sidepieces for like withdrawal. When the ingot is col-d, the cores areenga-ged at their projecting ends and stretched by tension thereon sothey are removed. Flattened hollow tubes maybe positioned in inclinedoverlapping relation in a mold, and ingot metal cast around them forbonding them to an integral Whole ingot: this practice being ofparticular advantage when the tubes a-re of a cladding metal such aspure aluminum wit-h the cast metal being an aluminum alloy, or ofstainless steel when the cast met-al is cheaper carbon steel. Anotherprocedure is to prepare plain strips of cross-sectional dimensions atleast equal to those of the inter-channel metal portions 17, 18, 19, 20,

'21 of FIIGURE 1, coating most of one s-urface of each strip with aresist such as flame-sprayed alumina or other refractory material, whileleaving a longitudinal marginal portion bare and of bondable metal,placing a pack of such strips in a mold while leaving such marginalportion exposed along with a like marginal width a-t the other surfaceof t-he individual strip at the other side of the pack, and castingmetal around the pack for bonding to the exposed margins of the stripsa-nd therewith presenting the-resist coatings as the channels 11, 12,13, 14, 15, 16 of FIGURE 1. Such billets may also be prepared byextruding through so-called blind hole dies, in which the metal isforced along like cores and passes therefrom in the illustrativemulti-channeled form.

This billet of FIGURE l is then subjected to a schedule of rolling andheat treatment, after a suitable anti-welding resist material has beenformed or is present in the channels 11, 12, 13, 14, and 16. Such resistmay also be employed in the notches 26, but is not usual- =ly necessary,noting that surface lubrica-nts are customarily employed in rolling.Suitable resists are metal salts such as sodium and barium chloridewhich undergo lthe phenomenon called cold flow under the pressure andtemperature of rolling. Organic high molecular substances such assilicones, metal stearates, polymers of et-hylene linkage structure,polycarbona-tes, epoxy resins, and phenol aldehyde resins are usable.Dependent upon the met-al and the conditions of rolling, refractorypowder resists such as mica, talc, graphite, aluminum and other metaloxides can be employed.

As a result of a schedule of hot and cold rolling, the strip S of FIGURE2 is produced, in which the primed numerals are employed as in FIGURE 1to show the relationship of the corresponding parts after they have beenreduced by rolling. As a result of the reduction in thickness withextension of length, the channels become essentially closed upon thinresidual layers of the likewise extended resist material, and theirangles relative to the billet surfaces are flattened. The metal portions17 '-21' are correspondingly reduced in thickness in the strip S. Thenotches l26' are likewise closed and reduced in height but remainessentially opposite the outer ends of the channel residues 11,`16'.

The strip has smooth surfaces, and the locations of the channel residues26 are essentially invisible; and the residues 11, 12', `13','1l', 15',16 are likewise essentially invisible at exposed cross-sections producedby cutting the strip transversely. 'Howeven these external notchresidues 26 provide weaknesses in the rolled strip, and can now bebroken through by flexing as indicated in FIGURE 3, so that theseparation occurs along longitudinal lines determined by the positionsof the notches 26, in the original billet of FIGURE 1, and then bytension, `as shown by the arrows, in opposite direction-s upon thelateral portions 22', 23' of the strip, the continuous surface metalportions 24', 25' are caused to shift laterally with respect to oneanother, wherewith the metal wall portions or layers 1'7'-21, locatedbetween pairs of the resist residues of the original channels, rockessentially about their end connections to the surface metal as fulcra.Therewith, the distances between the rolled surfaces of the strip S areincreased.

Ultimately, as shown in FIGURE 4, the metal wall portions or septa 1?'21' can be brought to essentially right angles to the outer surfaces ofthe strip, and therewith form a series of channels 12"-15" which are ofa `general quadrilateral shape. The upper and lower walls of thesepassages or channels are not parallel to the outer surfaces of the stripS, but are at an angle thereto corresponding to the angle occupied bythe resist residues of the channels 11-16 as shown in FIGURE 2. Thewalls 1721' are of essentially uniform thickness in the illustrativeform.

The product thus made may have any desired number of channels 11'-16' inthe original billet, and a corresponding number, less two, of passages12"-15" in the finished structure. The height of the respective walls1721', and .thus of the individual passages, is determined by the amountof overlap of the channels 11-16 in the original billet: and the ratioof thickness of the individual walls 11W-21 to the average thickness ofthe surface metal portions 24', 25 of the opened strip is determined bythe ratio of the distance between lines a and b to the total billetthickness, noting that the lines a and b extend tangent to the tops andbottoms of the channels in the illustrative form, and define the surfacemetal portions 24', 25 which extend from side to side of the billet, ascompared to the central portion between the lines a and b which containsthe overlapping channels.

Such a structure forms a member which can be employed for structuralpurposes, as a wall or stiffener: and can also be used in the form shownas a conduit, for example, for heat exchange.

Where small heat exchange bodies, such as those for the evaporators ofmechanical refrigerators, are to be made, the extending thicker ends22', 23 of the opened strip of FIGURE 4 can be cut away, leavingportions extending laterally from the walls 17', 21', and these portionscan then be brought together as shown in FIGURE 5 and joined by cementor by welding.

A heat exchange body having an upper inlet and a bottom outlet is shownin FIGURE 6 as comprising a structure prepared from a body as in FIGURE5, with the end septum walls 27 left for the full length, while theintervening walls 28 have their ends excised or cut away, between thesurface metal portions 24;', 25' to provide connecting spaces 29. Theends of the body are then provided with closing walls 34, 36 havingrespective conduit connections 35, 37. These end walls may be assembledas shown in FIGURE 6-A, where an end wall 34 has the turned anges 34aclosely tting the surface metal portions 24, 25 and sealed thereto. Inthe structure of FIGURE 6, a fluid entering at 35 is distributed in thespace 29, which operates as a manifold, and then passes downward in theseveral passages, being collected again at a lower manifold portion 29,and passing out through the conduit connection 37. In FIGURE 6, theconnection at the pinched lips 3@ is illustratively by spot-welding atpoints 31.

In the form of heat exchange device shown in FIGURE 7, the generalsection and the end septum Walls 27 are as in FIGURE 6, but inthis casealternate intermediate walls 38, 38 are clipped at the bottom and theintervening walls 39, 39 clipped at the top, all between the surfaceportions 24', 25'. End walls 34, 36 with conduit connections 35, 37 areprovided as before. Illustratively, in this form, the pinched lips 30are connected by a roll-forged seam 32 at each lateral edge. In thisstructure, a fluid entering at connection 35 passes in zigzag fashion asshown by the arrows, and issues from the other conduit connection 37.

The same principle can be employed for providing a body having a numberof rows of lonigtudinal passages. Thus, in FIGURES 8-10, two such rowsare provided.

In FIGURE 8, the billet Ba is provided with two rows of inclinedchannels 11-16, each with the intervening metal portions 17-21. Thelongitudinal notching grooves 26 are provided as before, in alignmentwith the outer ends of the lateral channels 11: while the other lateralchannels 16 are extended by horizontal branches 41, 42 for the lower andupper rows of channels, noting that these branches 41, 42 terminateshort of the lateral sides of the billet Ba. Above the respectivebranches 41, 42 are the metal end portions 22a, 23a: while below themare the metal end portions 22h, 23h. The roll engaging surfaces of theingot are provided by the solid metal portions 24, 25 as in FIGURE l,these being in parallel planes. At the median plane of the billet,represented by the dotted lines M-M, there is also a continuous metalportion 43, extending from side to side of the billet.

Upon rolling this billet to the strip Sa as shown in FIGURE 9, theproduct is much as in FIGURE 2, except that two sets of overlappedresist residues respectively above and below the median plane M-M areprovided from the channels 11-16 with intervening metal portions 1'7-21.The surfaces of the strip Sa of FIGURE 9 are planes and are provided bythe metal 24, 25: while a median continuous strip of metal extends fromside to side, between the two rows of resist residues.

For opening the strip of FIGURE 9, its lateral edges may be cut away atplanes illustrated by the upright lines 44, these cuts extending throughthe residues of the channel extensions 41, 42, and thereby giving accessto these channel residues at the edges of the strip. By bending theedges of the strip to separate the remaining parts of the metal portions22a', 22b' and 23a', 23b', and exerting tensions on the portions 2217'and 23a as indicated by the arrows, the structure may be opened to theform shown in FIGURE 10. Therewith, opposing tension on the parts 22a',23b can be employed to assure the proper positioning of the interveningwalls 17'-21 of the two series shown. Here, as with FIGURE 4, theindividual walls 17'-21 are of uniform thickness in the illustrativepractice and are directed at right angles to the outer surfaces providedby the metal portions 24'-25, noting that the inner surfaces of thesemetal portions have the inclined direction as before. The openedstructure thus has the two rows of channels as shown in FIGURE 10.

By employing more than two rows of channels 11-16, it is obviouslyfeasible to prepare a cellular body having any number of rows ofchannels as may be desired.

The principle can also be employed for the making of bodies havinginternal passages and external fins.

In the practice of FIGURES l1 to 13, the billet 50 has the inclinedoverlapping channels 11416 as before, with the end channels having theextensions 41, 42. Between these channels are the metal portions 17-21as before. Inclined grooves 51 are cut into the upper and lower surfacesof the billet 50 and, in the illustrative form, the grooves are slits ofuniform width and depth with the inner ends of the grooves 51respectively aligned with the ends ofthe internal channels 11-16, asshown by the dotted lines c.

When the billet of FIGURE 11 is rolled, with antiwelding resist in thechannels 11-16, and preferably also in the grooves 51, a strip Sb as inFIGURE l2 is produced in which the internal residues 11'16' have themetal wall portions 17'-21 between them: and a series of metal scales 52are formed on the upper and lower surfaces of the strip Sb of FIGURE l2,overlying the respective residues S1 of the grooves 51. When the stripSb is cut along planes such as that shown by line 44 with intersectionof the residues of channel portions 41, 42 at the two edges, and opened,a structure as in FIG- URE 13 can be formed. Therewith, the scales 52have been raised substantially to right angles and thus providelongitudinally extending iins parallel to one another and to the septumwalls 17', 18', 19', 20' provided by the metal from the correspondingparts of the billet in FIGURE l1. Between the septum walls and the nsare continuous laterally extending metal portions 24a, 25a which .are ofessentially uniform thickness between the ns, but are inclined relativeto the general horizontal lateral plane of the body shown in FIGURE 13,in general as described above for FIGURES 4 and l0. Between the internalwalls 17', 18', 19', 20' are the individual channels 12", 13" and 14".

As an illustrative practice under FIGURES 1-4, the billet may be threeinches thick after scalping. The channels 11-16 can be one-eighth of aninch thick, and 1.4 inches wide so that the distance between lines a andb is about one inch with the channels extending at an angle of about 45degrees to the horizont-al and thus overlapping by half their respectivehorizontal extensions. When this is rolled to a final strip S as inFIGURE 2 having a thickness of 0.040 inch, the face layers 24', 25' havean average thickness of 0.015 inch each, while the septum walls 17'-21are about 0.010 inch each, noting that their surfaces are at a verysmall angle relative to the strip surfaces. These walls overlap, in thestrip, by about one inch: so that when the strip is opened into thechanneled body of FIGURE 4, the internal wall spacing of the respectiveupper and lower 'body Walls is about one inch: and the quadrilateralpassagesV have a section of about one inch by one inch. With the samedimensions in FIGURE 1l, and the surface grooves 51 thin and cut forabout half the depth of the surface metal, the -cell dimensions are thesame, and the fins 52 of FIGURE 13 are about 0.007 inch thick at theirbases and extend about an inch.

FIGURES 14 to 16 show a procedure like that of FIGURES 8 to l0, forproducing articles having more than one row or layer -of cells in itsthickness. In FIG- URES 14 to 16 the two rows of original channels 11-16are arranged symmetrically or in herringbone fashion relative to oneanother, converging toward the median plane M. The billet 40a has thesurface grooves 26 located opposite the outer ends of channels 11, and afurther internal separation channel 42a is provided at the median planeM, illustratively of T-shape with the stem directed toward butterminating short of the lateral surface of the billet, and with thecross-bar extending from the median plane toward the rollengagedsurfaces of the billet. This cross-bar thus is adjacent lbut spaced fromthe inner ends of the channels 16, with its ends above Iand below theplanes c, d of the inner ends of the rows of channels. Upon rolling, thestrip Sd of FIG- URE 15 is formed: which, upon cutting -along the planeof line 44, permits engagement of the two lateral masses 22d', 23d' andthe employment of laterally directed tensions thereon, opposed Ibyengagement with the lateral mass 22)" at the other side, and the openingof the structure to the form shown in FIGURE 16, noting that theweaknesses adjacent the mass 22j', produced by the adjacency of therespective residues of a channel 11' and a groove 26' permit tearing -orbreakage so that the surface bodies 24', 25 are freed for movement fromone another and from the median body 43'.

FIGURES 17-19 show a practice corresponding to.

that of FIGURES 11-13, for forming -articles having lnternal channelsand external tins. Here the external grooves 51 are symmetrical, andwith rolling by feeding the billet to the roll nip in the transversedirection shown by the arrow permit a preliminary widening of the billetbefore, longitudinal rolling is done to bring the billet to the desiredfinal thickness. Likewise, the surface grooves 51 can be at low anglesto the roll-engaged surfaces, and can overlap one another as shown. Thestrip of FIGURE 18, thus produced, can then be opened to the form shownin FIGURE 19. When the grooves 51 of the billet overlap, as shown inFIGURE 17, the ribs 52 `are higher than the spacing between ribs, andcan have the composite shape of essentially uniform thickness adjacentthe lbody layers 24a', 25a', and tapering at their margins.

The operation of opening the rolled strip into multicellular form issimple; and the ns when present can be raised by mechanical operations.A preferred manner of raising the fins is illustrated in FIGURE 20,where a strip Sb as in FIGURE l2 is subjected to surface blasting withparticles as in shot-peening, e.g. as indicated by the arrows 80. An airblast ofy such particles acts differentially on thicker and thinnerparts of the scales, so that the edges are raised as shown by the dottedlines 51a, thus providing easy entry and engagement with their lowersurfaces by knife-like edges for completing the lifting to the uprightposition without damage to the edges. Such shot-peening and edge liftingcan be effected lby moving the article opposite a transverse row 81 ofblast nozzles, e.g. in the direction of the arrow 82.

The ingots can be prepared in various ways, and billets prepared otherthan by casting can be employed for the purpose. For example, metalstrips of a material not bonded by the ingot metal can be held spaced inproper position in an ingot mold, and the ingot metal cast around them.For example, with aluminum, stainless steel strips can be employedhaving a dimension of one-eighth inch thick by 1.4 inches wide in theabove illustrative practice. Alternatively, refractory resist powders,such as talc,

chalk, mica, graphite, lime, aluminum oxide, and other refractorymaterial can be formed into bars and positioned in a mold and the metalcast around them to form ingots of the desired cross-section. When thechannels are thin, it is preferred to form them by the use of thenon-welding metal core strips, which are then placed under tension inthe cold ingot, so that they may be pulled therefrom and leave thechannels: or by use of flattened integratable tubes: these channels canthen be lled with anti-welding material, followed by closure of the endsof the ingot and subjection to the desired schedule of hot andcold-rolling.

The procedure permits the use of ductile metals such as aluminum and itsalloys, steels of carbon and alloy types, copper and copper alloys'including brass and bronze, tin, for making cellular structures with orWithout external fins, which are monolithic and present surfaces of theselected metal and thus having the same electrochemical resistance, andcompetent of retaining, in the finished article, the work-hardeningeffects of cold working.

The strips rolled from the `billets can be coiled, stored, shipped andsold as articles of commerce. They can -be cut to desired lengths andthen expanded, lbefore or preferably after raising the fins whenpresent.

The invention is not limited to the illustrative practices and productsshown, `and may be employed in many ways within the scope of theappended claims.

What is claimed is:

1. An article of manufacture comprising a rolled metal strip havingopposed rolled surfaces and being of essentially uniform thickness andhaving internal angularly directed and overlapping first longitudinaldiscontinuities between metal portions extending from side to side 0fthe strip, and having angularly directed longitudinal seconddiscontinuities extending inwardly from said 4opposed rolled surfacesthereof, said second discontinuities defining between them integralscales having thin edges at said surface and being thicker at the regionof integration with the said metal portions overlying the internaldiscontinuities.

2. An article of manufacture comprising a rolled metal strip ofessentially uniform thickness and having internal angul-arly directedand overlapping first longitudinal discontinuities between metalportions extending from side to side of the strip, and having angularlydirected longitudinal second discontinuities extending inwardly from arolled surface thereof, said second discontinuities deiining betweenthem integral scales having thin edges at said surface and being thickerat the region of integration with the said metal portions overlying theinternal discontinuities, each of said second discontinuities beingdisposed in overlapping arrangement with an adjacent one thereof.

References Cited by the Examiner .UNITED STATES PATENTS 2,597,343 5/1952Lang 29-19O X 2,981,520 4/1961 Chadburn 165-170 2,996,792 8/1961 Mackie29-157.3 3,205,560 9/1965 Lochlein 165-170 X FOREIGN PATENTS 237,974 10/1959 Australia. 1,191,345 4/1959 France.

159,933 3/ 1921 Great Britain.

vROBERT A.y OLEARY, Primary Examiner.

M. A. ANTONAKAS, Assistant Examiner.

1. AN ARTICLE OF MANUFACTURE COMPRISING A ROLLED METAL STRIP HAVINGOPPOSED ROLLED SURFACES AND BEING OF ESSENTIALLY UNIFORM THICKNESS ANDHAVING INTERNAL ANGULARLY DIRECTED AND OVERLAPPING FIRST LONGITUDINALDISCONTINUITIES BETWEEN METAL PORTIONS EXTENDING FROM SIDE TO SIDE OFTHE STRIP, AND HAVING ANGULARLY DIRECTED LONGITUDINAL SECONDDISCONTINUITIES EXTENDING INWARDLY FROM SAID OPPOSED ROLLED SURFACESTHEREOF, SAID SECOND DISCONTINUITIES DEFINING BETWEEN THEM INTEGRALSCALES HAVING THIN EDGES AT SAID SURFACE AND BEING THICKER AT THE REGIONOF INTEGRATION WITH THE SAID METAL PORTIONS OVERLYING THE INTERNALDISCONTINUITIES.